getting below error after calling the web service

Summary:

We are trying to fetch Due date of a service request . to implement this , we are using web service.But while fetching the data , it is giving below error :

Content (please ensure you mask any confidential information):

web service : get request on service request data , auth id used is also correct

url

https://fa-erqw-test-saasfaprod1.fa.ocs.oraclecloud.com/crmRestApi/resources/11.13.18.05/serviceRequests/##SrNumber##

Object function which is being invoked from object workflow :

def duedate = adf.webServices.FetchDueDate

try{

def duedatevalue = duedate.GET(SrNumber);
println('duedate is '+ duedatevalue);
}
catch(Exception ex)
{
throw ex;
}

set the workflow as on create. Getting below error :